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Bureau of Mines Information Circular/1984 



Microcomputer-Based Monitoring 
and Control System With Uranium 
Mining Application 

By C. T. Sheeran and J. C. Franklin 




UNITED STATES DEPARTMENT OF THE INTERIOR 



miMMB 



Information Circular 8981 

I* 



Microcomputer-Based Monitoring 
and Control System With Uranium 
Mining Application 

By C. T. Sheeran and J. C. Franklin 







UNITED STATES DEPARTMENT OF THE INTERIOR 
William P. Clark, Secretary 

BUREAU OF MINES 
Robert C. Norton, Director 




o(d 






Library of Congress Cataloging in Publication Data: 



Sheeran, C, T. (Christopher T,) 

Microcomputer- based monicoring and control system with uranium 
mining application. 

(Information circular / United States Department of the Interior, 
Bureau of Mines ; 8981) 

Bibliography: p. 24. 

Supt. of Docs, no.: I 28.27:898*1. 

1. Uranium mines and mining— Safety measures— Data processing. 
2, Microcomputers. 3. Real-time data processing. I. Franklin, John 
C. II. Title. III. Series: Information circular (United States. Bu- 
reau of Mines) ; 8981. 



-TN^5,U4 [TN490.U7] 622s [622'.8] 84-600091 



^ CONTENTS 

'^ Page 

Abstract 1 

Introduction 2 

System description 3 

rT^ Hardware 3 

^ Central processor 3 

v^ Data-event printer 4 

Communication trunk 4 

Accessors 4 

Binary accessors 4 

Analog accessors 5 

Modems 9 

Software 9 

Operating system 9 

Application software 9 

Main scan program 11 

Command service. 14 

Alarm printer service 14 

CRT display service 14 

Event sequencing 16 

Installation 17 

System use 18 

Startup procedure 19 

Data entry 20 

Operation 20 

Uranium mining applications 23 

Records 23 

Sequences 23 

Conclusions 23 

References 24 

Appendix. — Analog accessor calculations 25 

ILLUSTRATIONS 

1 . Basic system hardware 3 

2. Pulse-integrating accessor and continuous working level monitor 6 

3 . Functional block diagram of PI accessor 8 

4 . System memory map 10 

5 . Status from different accessor types 11 

6 . Flow diagram of scan procedure 12 

7 . CRT display areas 15 

8. CRT data display 15 

9 . Block diagram of surface equipment hookups 18 

TABLES 

1. Accessors evaluated for uranium mining applications 5 

2. Count period dipswitch assignments for pulse-integrating accessors 7 

3. System commands sorted by function 21 





UNIT OF MEASURE 


ABBREVIATIONS USED 


IN THIS REPORT 


ft/mln 


foot per minute 


min 


minute 


h 


hour 


ms 


millisecond 


in 


inch 


pet 


percent 


kHz 


kilohertz 


s 


second 


km 


kilometer 


V ac 


volt, alternating 
current 


L 


liter 










V dc 


volt, direct current 


m 


meter 










WL 


working level 


MeV 


million electron 








volts 


WLM 


working level month 



MICROCOMPUTER-BASED MONITORING AND CONTROL SYSTEM 
WITH URANIUM MINING APPLICATION 

By C. T, Sheeran and J» C« Franklin 



ABSTRACT 

The Bureau of Mines investigated a microprocessor-based real-time con- 
trol and monitoring system for uranium mining applications. The system 
is capable of controlling and monitoring up to 768 stations within 3 km 
of the central processor on a common four-wire cable. It can be used in 
conjunction with detectors to continuously monitor and display radiation 
working levels at points throughout the mine. Surface alarms are sound- 
ed for critical situations such as rapid radiation buildup, loss of pow- 
er to monitors or fans, and changes in air door position. Permanent 
records of all changes are automatically printed out with their time of 
occurrence. Printouts can also be obtained for shift reports or trend 
logs. The system can be used to remotely control fan startup and shut- 
down, and also can alert miners of underground conditions by blowing 
horns or turning on lights. Battery backup keeps the system operative 
for up to 4 h in case of a mine power outage, A special software fea- 
ture permits automatic, time-delayed, sequential restart of fans. 



^Mining engineer, 
^Supervisory physical scientist. 
Spokane Research Center, Bureau of Mines, Spokane, WA. 



INTRODUCTION 



In protecting the health and safety of 
underground personnel, the mining indus- 
try must contend with the radioactive gas 
radon and its daughter products. Radon 
and radon daughters are decay products of 
uranium and are found in nearly all types 
of mines. However, the extreme concen- 
trations of these daughters in uranium 
mines present a greater health hazard 
than that found in other types of mines. 

The radon daughters polonium-218 and 
polonium-2lA emit alpha particle radia- 
tion that may induce certain forms of 
cancer. Exposure to these daughters in 
mine air has been shown to produce a high 
incidence of lung cancer among uranium 
miners (J_).^ Present Federal safety 
standards state that the maximum allowa- 
ble concentration of radon daughters in a 
work environment is 1 WL unless respira- 
tors are worn. Total exposure per person 
is limited to 4 WLM for any calender 
year.^ 

Most of the uranium produced in the 
United States is mined from sandstone 
formations, which have high porosity and 
permeability and which may be highly 
fractured. Because of this, radon is re- 
leased from the sandstone very readily, 
and its emanation rate can be profoundly 
increased by a slight decrease in baro- 
metric pressure. 

Ventilation techniques that employ 
blowing, exhausting, and push-pull fan 
combinations are used by the industry to 
supply adequate air quantities to reduce . 
the radon daughter concentrations. As 
uranium mines have become larger and 

■^Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendix. 

'^One working level is defined as any 
combination of short-lived daughters in 
1 L of air that will result in the ulti- 
mate emission of 1,3 x 10^ MeV of alpha 
energy. This includes the radon daugh- 
ters from polonium-218 through polonium- 
214. The working level month is defined 
as the working level exposure multiplied 
by the hours exposed, divided by 173. 



deeper, and electrical costs have 
risen, ventilation costs have increased 
sharply — ventilation now accounts for a 
major portion of underground uranium mine 
production expenditures. Bates (2^) es- 
timated that in order to comply with the 
4-WLM standard, these costs ranged from 
$4.68 to $5.41 per ton of ore removed 
in 1980. This estimate included costs 
for electricity, ventilation shafts, 
fans, vent bags, and other associated 
equipment . 

An interruption in mine power, causing 
fan shutdowns, can produce drastic 
changes in the radon and radon daughter 
concentrations. Sometimes shutdowns may 
go undetected for some time. Franklin 
(3^) and Musulin (4-5^) have shown that fan 
shutdowns of 5- to 30-min duration can 
increase radon concentration to three to 
five times normal, Franklin (6^) reports 
that the mining activities of slushing 
and blasting may increase this concentra- 
tion up to 40 and 400 pet, respectively. 

The uranium industry presently uses 
Kusnetz sampling to determine personnel 
exposure and to detect areas where ven- 
tilation changes are needed to maintain 
desirable radon daughter levels. These 
samples are taken at various intervals 
ranging from daily to monthly, depending 
on radiation concentration and sampler 
availability. Kusnetz-type samples are 
usually very accurate point-in-time mea- 
surements. However, since concentrations 
are continually changing, more continuous 
methods of monitoring are needed to mini- 
mize miner exposure. Continuous monitor- 
ing can provide data never before availa- 
ble to ventilation engineers, which can 
be used to optimize the ventilation 
network. 

The Bureau of Mines has been investi- 
gating instrumentation that can help in 
detecting excessive working levels. 
Droullard (7) devised a continuous work- 
ing level monitor that has been used for 
several years in the Bureau's research 
activities in both experimental and 
active mines. Shaw and Franklin (8^) took 
this continuous working level monitor and 



interfaced it to a microcomputer to cre- 
ate an alarm system, which has been suc- 
cessfully field-tested. It was concluded 
from the field test that an alarm system 



with expanded capabilities would be more 
useful to the ventilation engineer. 
Therefore, work began on the new system 
described in this report. 



SYSTEM DESCRIPTION 



The system investigated is a modified 
Senturion-2005 manufactured by Conspec 
Controls, Ltd. Modifications were per- 
formed by Conspec in both hardware and 
software according to Bureau specifica- 
tions, and the Bureau has made further 
hardware modifications to the system for 
mine use. Much of the following informa- 
tion was derived from Conspec manuals 
(9). 

HARDWARE 

The Senturion-200 is advertised as 
a "microcomputer-based real-time data 

^Reference to specific trade names and 
manufacturers is made for identification 
purposes only and does not imply endorse- 
ment by the Bureau of Mines. 



acquisition, monitoring, and control sys- 
tem." Its basic hardware consists of a 
central processor, data-event printer, 
communication trunk, and accessors , as 
illustrated in figure 1. Modems may also 
be included with the system for long- 
distance operation. 

Central Processor 

The central processor is a desktop 
unit that contains the main processor, 
video terminal (CRT), keyboard, disk 
drive, and accessor trunk drivers. The 
main processor is a Zilog-based microcom- 
puter system that uses a Z80A central 
processing unit with both parallel and 
serial input-output (I/O) ports. Memory 
consists of 65,536 (64K) bytes of dynamic 
Accessor 




Accessor 



FIGURE 1. - Basic system hardware. 



random-access memory (RAM) , with an addi- 
tional 7.168 (7K) bytes of erasable, pro- 
grammable read-only memory (EPROM) . A 
floppy-disk controller is used to inter- 
face to the system disk. Other compo- 
nents include direct memory access (DMA) 
logic, an on-board programmable read-only 
memory (PROM) programmer, and a four- 
channel counter-timer. 

An Intel 8080 microprocessing unit is 
used to control the CRT and keyboard. 
The alphanumeric keyboard is similar to 
the keyboard of an office typewriter, 
with additional special function keys 
used to simplify operator commands when 
in the main program. 

The system disk uses 8-in, single-sided 
floppy disks and provides 131,072 (128K) 
bytes of additional memory. Disks are 
used as nonvolatile storage for programs 
and data. 

Data-Event Printer 

A Teletype 43RO printer is used with 
the system for character-at-a-time , 
receive-only operation. The system is 
programmed for automatically and manually 
requested printouts. Automatic printouts 
are obtained for all alarms and events 
with their corresponding time of occur- 
rence. The printer can also be requested 
from the keyboard to print descriptions, 
shift reports, trend logs, and other sys- 
tem configurations and parameters. 

Communication Trunk 

The communication trunk is a data chan- 
nel through which the system communicates 
with the accessors. The trunk is con- 
nected to the central processor via an 
RS-232 interface and to the accessors via 
a single four-wire shielded cable. The 
trunk uses two of these wires to provide 
24-V dc power to the accessors; the re- 
maining two wires are used to transmit 
and receive digital signals. Trunk- 
to-accessor communication is asynchronous 
at 4,800 baud. 



Accessors 

Accessors manufactured by Conspec pro- 
vide the interface between the system and 
the field devices to be monitored or con- 
trolled. At the heart of each accessor 
is an addressable universal asynchronous 
receiver and transmitter (UART) chip. 
This chip has an asynchronous data format 
consisting of a serial stream of data 
bits preceded by a start bit and followed 
by a stop bit. The UART receives two 
eight-bit words in a serial data stream 
from the processor; the first word re- 
ceived is an address , and the next is a 
command. When the address sent matches 
the programmed address of the receiver, 
the transmitter is enabled to transmit 
two data words consisting of accessor 
identity and status. 

Each accessor is actually a point mul- 
tiplexer with its own unique dipswitch- 
selectable address variable from to 
127. An identity (ID) dipswitch on the 
accessor card permits the user to select 
the binary word that will be used by the 
processor to interpret the incoming data. 

Accessors are classified as either ana- 
log or binary. Both types of accessors 
were purchased for field testing in ura- 
nium mining situations. Table 1 is a 
list of accessors evaluated with the 
system. 

Binary Accessors 

Binary accessors control and/or report 
status from contacts. Three kinds of 
these accessors were used in mine tests 
to perform such jobs as turning on mine 
fans, flashing warning lights, or turning 
on underground alarm lights . Binary ac- 
cessors used include the Bl, B2, and B25 
types. 

Bl Accessor 

The Bl accessor is used to monitor the 
condition of a field-mounted supervised 
contact. Each accessor can handle one 



TABLE 1. - Accessors evaluated for uranium mining applications 



Accessor' 



Type 



Data 

entry 

code 


ID dipswitch 
7 6 5 4 3 2 10 




1 

5 
4 


00000000 
00000000 

(2) 
10 10 
10 


7 
2 


1110 
10 



A5 (A). 

A8 (A). 

PI (A). 

Bl (B). 

B2 (BC), 



B25 (BC), 
B26 (AC), 



Process 

Potentiometric , 

Pulse-integrating. . , 

Single binary 

2-state commandable 

binary, 
5 output. ........... 

Setpoint (6 output). 



'Accessor classification: A = analog; AC = commandable analog 
B = binary; BC = commandable binary. 
2 Hardwired. 



function point and receives its input 
from a normally closed or normally open 
dry contact switch. Proper installation 
of end-of-line resistors enables the ac- 
cessor to monitor and detect sensor line 
faults. The contact sensor may be lo- 
cated up to 30 m from the accessor. 

The Bureau used this accessor as a 
bulkhead door position monitor, ventila- 
tion fan monitor, and mine power monitor. 
It has also been used in conjunction with 
the pulse-integrating accessor (analog) 
to detect power interruption and sensor 
line faults for the continuous working 
level monitors. 



from the surface. It could also be used 
in conjunction with a sequencing program 
to automatically restart fans in sequen- 
tial order after a power bump. 

B25 Accessor 

The B25 is a commandable accessor simi- 
lar to the B2, except that it can control 
up to five outputs. As with the B2, the 
accessor is used with an SRP to interface 
accessor circuitry to circuits having 
other voltages and currents. The B25 
accessor cannot be used, however, to give 
flow status; it can only be used to turn 
devices on or off. 



B2 Accessor 

The B2 accessor is used for command 
controlling of any two-state, remotely 
located field device. The accessor is 
used with a slave relay package (SBIP) to 
interface accessor circuits with other 
voltages and currents. Used together, 
the accessor and SRP can start and stop 
motors, open and close dampers, or con- 
trol other two-state functions. The ac- 
cessor can also be used to monitor status 
and alarm conditions of motors not di- 
rectly commanded from the terminal. When 
proof-of-flow status (verifying that de- 
vice state matches commanded state) is 
required, the accessor and SRP can accom- 
modate either an ac or dc contact switch. 

In Bureau tests, this accessor was used 
to control underground ventilation fans 



Although the B25 occupies one address, 
it contains five different, individually 
selectable points. This accessor has 
been used in conjunction with sequencing 
programs to provide a central alarm indi- 
cator in mine tests. In this capacity, 
it has been used to drive light-emitting 
diode (LED) indicators, which represent 
specified mine conditions such as a work- 
ing level alarm. The central alarm indi- 
cator was located to provide a quick 
visual determination of current alarm 
conditions for underground personnel. 

Analog Accessors 

Analog accessors convert analog signals 
or pulses from field devices to digital 
form. The digitized value is then sup- 
plied to the processor upon interroga- 
tion. Four different types of these 




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accessors were tested by the Bureau: 
A5 , A8 , B26, and pulse-integrating (PI) 
types. 

A5 Accessor 

The A5 is a process-type eight-bit ac- 
cessor that is used with a field device 
to monitor the condition of a dynamic 
process. The signals from the appropri- 
ate sensors are converted into analog 
values by a process transducer. The A5 
accessor will accept and digitize an ana- 
log value within the range of to 5 V 
dc. The process transducer may be lo- 
cated up to 160 m from the accessor with- 
out loss of accuracy. 

The Bureau has used A5 accessors with 
J-Tec anemometers and with temperature 
and relative humidity sensors. 

A8 Accessor 

The A8 is a potentiometric-type eight- 
bit accessor that is used with a remotely 
located potentiometric sensor. Such a 
sensor can be used to monitor pressures 
or the position of a damper or other de- 
vice. This accessor can be used with any 
three-wire, full-travel potentiometric 
sensor that has a full-scale span between 
2,000 and 10,000 ohms. The sensor may be 
located up to 160 m from the AS accessor. 

B26 Accessor 



was used with a sequence triggered by 
alarm conditions (such as working level, 
power-off , or sensor line fault) to turn 
on LED indicators. 

Pulse-Integrating Accessors 

The PI accessor card shown in figure 2 
was built by Conspec according to Bureau 
specifications. This 16-bit accessor was 
designed to interface to continuous radi- 
ation monitors designed by the Bureau to 
measure radon and working level concen- 
tration (7^, 11 ) . These monitors output 
random, transistor-transistor logic (TTL) 
compatible pulses; the number of pulses 
per unit of time is proportional to radi- 
ation concentration. 

A block diagram of the PI accessor is 
shown in figure 3. This accessor accepts 
the TTL-compatible pulses at a single in- 
put and divides the input pulse frequency 
by a selectable factor (prescaler) . The 
prescaler is selectable from 2 to 255 and 
is entered as an eight-bit binary number 
at dipswitch S22. After being divided by 
this factor, the pulses are fed to a 16- 
bit binary counter where they are accu- 
mulated for a fixed period of time (count 
period) . This period is selectable from 
0.4 to 819 s (13 min, 39 s) in increments 
of 0.2 s and is set as a binary number on 
dipswitches S20 and S25. Weights as- 
signed to each rocker switch are shown in 
table 2. 



The B26 accessor is a binary setpoint 
accessor with a resolution of six binary 
bits. It is similar to the B25 (binary) 
except that the outputs are not indi- 
vidually controlled. It is classified as 
a commandable analog accessor. The six 
outputs are controlled by position and 
have 64 different binary combinations of 
enabled or disabled states. Position 
corresponds to all outputs enabled; posi- 
tion 63 to all outputs disabled. This 
accessor can be used with other hardware 
logic to vary motor speeds or to adjust 
louvre positions. 

The B26 has been used by the Bureau to 
provide alarm indicator lights for the PI 
accessor. In this application, the B26 



TABLE 2. - Count period dipswitch assign- 
ments for pulse-integrating accessors 





Dipj 


switch 


Rocker 


Weight , s 


S25., 


4 
3 


409.6 








204.8 








2 


102.4 








1 


51.2 


S20.. 






8 

7 


25.6 








12.8 








6 


6.4 








5 


3.2 








4 


1.6 








3 


.8 








2 


.4 








1 


.2 



S22 



I I I I I I I I 



Pulse 



input 



Conditioner 



D ips w i t c h 
to select 
N (2-255) 



Prescaler -r N 



Reset 



^ 16-bit counter 



Latch 



16 
MSB 



-C-JZ 

bit latch 



LSB 



Time base 

generator 

0.4 s-13 min 



S20- 
S25 



UART 



MUX 



Select 



Clock 
307.2 kHz 



Mill lllllll 



Dips witch to 

select time 

base 



ID 
switch 



Address 
switch 



Data 
in 



ID in 

Address 
in 



5_i 



Trunk 
interface 



^ 



1 



To accessor 
trunk 



FIGURE 3. - Functional block diagram of PI accessor. (LSB = least significant byte; MSB = most 
significant byte; MUX = multiplexor.) 



The maximum accumulated count of this 
accessor is hardware-restricted to the 
15-bit count value of 32,767; the pre- 
scaler and count period should be se- 
lected to meet this requirement. 

Two LED's located on the accessor cir- 
cuit card indicate the presence of an 
input pulse train and count period re- 
set, respectively. These LED's, off in 
normal operation, are enabled by switch- 
ing rocker 8 of S25 to the on position. 



Troubleshooting and calibration proce- 
dures may involve the use of these LED's. 

When the PI is interrogated during the 
scan, it will provide the processor with 
the last completed accumulated total. An 
on-board 16-bit register is used to save 
this last completed count. Since the 
data transmission to the processor is 
byte oriented, the processor requires two 
interrogations to obtain the full 16 bits 
of data. 



The ID dipswitch of the PI accessor, 
unlike that of other accessors, is hard- 
wired and, therefore, not selectable. 
When this ID is received during an inter- 
rogation, the processor calls a special 
software routine to handle the two re- 
turned data bytes. The 8 most signifi- 
cant bits of the 16-bit total are then 
used in calculations and in alarm 
processing. 

Modems 

Points many miles away from the proces- 
sor, such as those at another mine, can 
be monitored and controlled through 
modems. The modems, called long-distance 
accessors (LDA's), consist of a local and 
a remote unit. The local LDA is connect- 
ed to the communications line as an ordi- 
nary accessor and requires 110-V ac pow- 
er. Data transmission between this unit 
and the remote LDA may take place on 
dual, metallic-shielded, twisted-pair 
conductors or on a half-duplex, leased, 
3,002 voice-grade telephone line. Dis- 
tance limitations are as follows: up to 
2.7 km with 18 American wire gauge (AWG) 
dual cable, and up to 6,400 facility km 
with the leased telephone line. Several 
remote LDA units can be used with a sin- 
gle LDA local unit. 

Each message sent between modems is du- 
plicated and slowed down to 600 baud. 
When receiving, the modems compare dupli- 
cate messages for errors , then increase 
transmission rate to 4,800 baud into the 
accessor trunk line. The remote LDA 
functions also as a remote accessor trunk 
by providing +24 V dc and 4,800-baud 
transmission to its connected accessors. 

SOFTWARE 

Senturion-200 software is made up of 
two parts: the operating system and ap- 
plication programs. The operating sys- 
tem used is a control program for mi- 
croprocessors (CP/M) (10). Applications 
programs written by Conspec accomplish 
data acquisition, monitoring, and control 
of the various points. 



Operating System 

CP/M consists of programs that execute 
user commands and access hardware re- 
sources such as the CRT and printer. The 
basic system executive and boot-strapping 
programs reside in EPROM memory to enable 
the CP/M to be transferred from disk to 
RAM on powerup, CP/M commands consist of 
both resident and transient directives. 
Resident commands are "built in" and can 
be used to read the current disk direc- 
tory (DIR) , erase files from the disk 
(ERA) , rename files (REN) , type out con- 
tents of a file to the CRT (TYPE) , and 
save the contents of memory as a file on 
the disk (SAVE), 

Transient commands such as DDT, ED, 
MOVCPMM, PIP, SYSGEN, and XDIR are known 
as utilities. These have a file type of 
,C0M and will appear in the directory if 
present. These commands enable the user 
to debug programs (DDT) , create and edit 
files (ED) , alter the CP/M image size 
(MOVCPMM) , copy files from one disk to 
another (PIP) , copy the CP/M boot onto 
new disks (SYSGEN), and look at files in 
alphabetical order with file size listed 
(XDIR) , 

These resident and transient commands 
are explained in detail in CP/M manuals. 

Application Software 

Once the CP/M is booted, the user can 
enter into application programs written 
by Conspec, These various programs per- 
form in concert with each other and com- 
prise the main program, A keyboard com- 
mand (see "Startup Procedure" section) 
begins the loading sequence, which first 
alters the RAM configuration and then 
loads files stored on disk. For the 
Bureau's system, the following files are 
loaded: 

1, S200BAS — main operating software, 

2, PRNIOP — printer-operation software, 

3, NLDAOP — modem-timing software. 



10 



4. SHRIOP — shift-report software. 

5. RADNOP — pulse-integrating accessor 

software. 

6. ESQ203 — event-sequencing software. 

After loading each of these files, the 
computer will display memory locations 



and other data. The locations corre- 
spond to slots in the startup procedure 
area shown on the Senturion memory map 
(fig. 4). When loading is complete, the 
main program starts and runs in a con- 
tinuous loop to perform the monitoring 
and control functions. While in this 
mode, only application commands are ac- 
cepted (CP/M commands are invalid) . 



FFFF 



Status 
saved on 
and read 
from disk 



Startup 



CP/M-DDT 



Special tables 



CF-OFS tables 



status buffer 



Scan buffer 



Alarm buffer 



Specials and 
custom software 



Main 
operating 
software 




Variables 
and flags 



Units and mode 
1/2, 3/4 tables 



I/O device 

buffers ( printer 

and CRT ) 



Reserved for 
CP/M 



Interrupt vector table 

and 
disk drive commands 



FIGURE 4. • System memory_ mop. 



11 



Application programs include the main 
scan program, command service, alarm 
printer service, CRT display service, and 
other software such as the sequencing 
program. 

Main Scan Program 

Once in the main program, the processor 
continuously sends messages to the acces- 
sors in a predetermined sequence. Mes- 
sages consist of an address and a command 
to which the appropriate accessor 
responds by returning its identity and 
status. Status consists of digitized in- 
formation, which may represent an analog 
reading or the position of contacts, as 
shown in figure 5. 

After requesting information from an 
accessor, the processor waits several 
milliseconds for data to be returned. 
During this time, it performs the remain- 
der of its tasks such as updating the CRT 



or performing calculations. If no data 
are returned, as in the case of broken 
communication lines, a communication-fail 
alarm is generated. The processor then 
continues with the scan, starting with 
the next address. A flow diagram of the 
scan procedure is shown in figure 6. The 
scan checks only those accessors that the 
operator has enabled through the key- 
board. Scan time per accessor is on the 
order of 10 ms; total scan time depends 
upon the number of enabled accessors on- 
line. The presence of modems in the sys- 
tem slows down the scan time. 

For binary points, received data are 
checked against the last valid reply re- 
ceived. If they match, the message is 
ignored and no updating of status occurs. 
With analog points, the received data are 
checked for normal or alarm condition, 
and the delay-to-alarm counter (up to 
255-s delay permitted) is updated accord- 
ingly. If there is a change in the data 



Central processor 




Accessor 
value 




Accessor 
value 



Contact 
status 



Command 



Contact 
status 



PI 
accessor 



B1 
accessor 



B2 
accessor 



Analog 
voltage 



Anemometer 



Pulses 




Contacts 



ANALOG 



— II — Normally open 
I '-^4f—' Normally closed 

BINARY 



Relay 



Fan 
motor 



<so^> 



FIGURE 5. - Status from different accessor types. 



12 




Update scan 
address counter 




Yes 



Set end-of 
scan flag 



Reset 
try counter 




Set 
transmit flag 



Transmit data 



Restart timer 



Main line 



r^ start J 



? 



FIGURE 6. - Flow diagram of scan procedure. 



13 




Increment 
trycounter 




Set up the 
error code 



Fill print 
CMD buffer 




Increment 
trycounter 



Retransmit 



^ 



^^1S\,Yes 


Transmit 




Restart 


^xecute^^^' 






timer 


|No 












JT 








^^D irN^ 
progress^ 




Set CMD 

progress 

flag 


Tno 











FIGURE 6. - Flow diagram of scan procedure -Continued. 



14 



received, the processor determines the 
nature of the change and records this in- 
formation in a temporary buffer. From 
there, the information is decoded and 
displayed on the CRT and printed if 
desired. 

Command Service 

Command requests may originate from 
either the keyboard or from a programmed 
event sequence. It is possible for both 
to be in simultaneous operation on a 
time-share basis. Command requests are 
prioritized when issued, and a system 
executive processes them for priority 
before passing them to a command execu- 
tion routine. A successful execution is 
printed out as an event on the printer 



and also displayed as a status change on 
the CRT. If a command initially fails, 
the processor will try again twice more 
before printing out a code of the failure 
on the printer. 

Alarm Printer Service 

The user determines at the time of data 
entry whether a point's events will be 
printed. It the print option is chosen, 
an occurring event (change of state) 
causes an internal buffer to be filled. 
These data are then transferred to the 
printer. The format observed for these 
messages is shown below, followed by an 
example printout for both binary and ana- 
log points. 



TIME 


PT. NO. 


DESCRIPTOR 


MODE 1/2 


MODE 


3/4 


STATUS 


10:19:30 


30 


965 FAN MONITOR 


ON 






NORMAL 


11:14:01 


17 


WL#207 (ESCAPE) 


HIGH 






ALARM 


13:09:00 


17 


WL#207 (ESCAPE) 








NORMAL 


14:00:42 


1 


807 COM. FAN 


OFF 






ALARM 


15:33:58 


1 


OFF 




COMMD 


EXEC 




15:33:58 


1 


807 COM. FAN 


OFF 






NORMAL 



VALUE 



1.0004600 WL 
0.9923400 WL 



STATUS indicates the condition of the 
point and will be one of the fol- 
lowing: NORMAL, ALARM, communications 
failure (C.FAIL), communications restored 
(CREST), sensor lines open (SLO), or 
sensor lines closed (SLC). For analog 
points , the alarm status may have an 
identifier such as HIGH, LOW, or RATE. 

CRT Display Service 

The CRT screen is divided by software 
into five display areas , as shown in fig- 
ures 7 and 8. Area 1 contains 12 lines 
reserved for critical change-of-state 
conditions. As these conditions occur, 
the processor enters the data in this 
area and denotes recent entries with a 
flashing caret (<) to the right of the 
data. The user may acknowledge the event 
by pressing the special ACK key on the 
keyboard, and the caret will disappear. 
If the event is an alarm condition, a 
horn may sound, which is silenced by 
pressing the SIL key. Since the CRT can 



display only 12 of these lines at a time, 
software provision has been made to store 
remaining alarms in a temporary buffer 
until CRT space becomes available. In 
this case, the cursor (*) located to the 
left of the events will blink. The dis- 
play can be edited by positioning the 
cursor to any point with the UP and DOWN 
keys, and deleting the line with the DEL 
key. Waiting lines will automatically 
appear at the bottom of the display area. 
For protection, it is impossible to 
delete lines if unacknowledged events are 
present. Alarms are displayed in reverse 
video format (black letters on a white 
background) for easy identification. 

Area 2 is reserved for user communica- 
tion with the computer. Keyboard inputs 
are echoed in this area, which is also 
used by the processor to prompt for data 
entry. All invalid input is ignored by 
the program. User commands consist of 
three-character mnemonics , some of which 
are entered by pressing special keys. 



15 



Area 
1 



Area 
2 



Area 
3 



Critical alarm 

Displays up to 12 alarms and 
return to normal conditions 
simultaneously. Alarms are 
displayed in reverse video 
format 



Operator data request and/or 
reply, keyboard input echo 



Continuous status monitoring area 

Up to 6 analog or binary points ma 
be displayed and continuously update 



Area 4 


Date 


Time 



Sequencing 

Displays 

sequence 

numbers 

currently in 

operation 



Area 5 



FIGURE 7. - CRT display areas. 




FIGURE 8. - CRT data display. 



16 



Area 3 contains six lines reserved for 
monitoring continuous status. Any point 
chosen for display in this area will be 
continuously updated with current analog 
value or binary status. 

Area 4 is serviced by a special program 
to display the current time and date. 
These are set by keyboard commands. 

Area 5 is reserved for event-sequencing 
activity. Any sequence currently in 
operation will be displayed in this area; 
also, interrupted sequences sorted in 
order of priority will be noted. 

Event Sequencing 

The event-sequencing software allows 
the user to program a series of events 
with associated time delays. These se- 
quences may be started either manually 
(with the ESQ command) or automatically. 
Automatic sequencing is accomplished by 
setting a software trigger to initiate 
the sequence, A trigger is a specified 
condition for a point; when the point 
changes status to this condition, the 
corresponding sequence is initiated by 
the processor. Changes of state permit- 
ted for triggering include normal, alarm, 
high alarm, low alarm, mode 1 (on) , mode 
2 (off), and communication failure. In 
mine situations, event sequencing has 
been used to restart fans after power 
bumps and to control LED indicators rep- 
resenting alarm conditions. 

The sequencing software contains 255 
sequence processing units (SPU's), Each^ 
SPU has the following structure: 

Header (contains SPU number, prior- 
ity, and hold status). 

Event 1. 

Event 2, 



Event 3, 



Link, pointer (points to another SPU). 



Up to eight SPU's can be 
any one time; when more 
been activated (queued) , 
and performed according 
ority, SPU's can be 
length by using the link 
to another SPU. 



in operation at 
than eight have 
they are sorted 
to their pri- 
chained to any 
pointer to point 



A sequence event can be one of three 
types: a test, a command, or a null 
event, A test event within a sequence 
may be applied to any point in the sys- 
tem and is used to direct the flow of 
the sequence. Conditions that can be 
tested include normal, alarm, communica- 
tion failure, and less than, equal to, 
or greater than a test value. Condition- 
al jumps or calls may be chosen as a re- 
sponse to the test result, A jump di- 
verts the sequence to another SPU if the 
test condition is false, A call performs 
another sequence as a subroutine when the 
test condition is true. Call depth is 
limited to four calls within prior calls. 

Commands in a sequence behave in the 
same manner as operator commands entered 
through the keyboard. Although any type 
of accessor may be tested, only commanda- 
ble accessors such as the B2, B25, and 
B26 types may be commanded. Time delays 
up to 255 s may be Included with a com- 
mand event. 

A null event produces no action except 
continuation of the sequence during pro- 
cessing. Null events are desirable be- 
cause of programming considerations. 

In area 5 of the CRT display are eight 
reserved lines, which correspond to eight 
activity nodes present for sequencing. 
As a sequence is queued, it appears in 
this area in the following form: 



17 



start SPU# * current SPU# * current event#. 



When all eight lines are filled with 
operating sequences, new sequences will 
be held until an activity node becomes 



free. A higher priority sequence will 
temporarily interrupt a lower priority 
sequence when all nodes are in use. 



INSTALLATION 



As part of the installation process, 
planning must take place to decide on 
sensor locations and which fans to moni- 
tor and control. The actual installation 
of the system in a mine typically con- 
sists of stringing the cable; installing 
accessors, monitors, and protection de- 
vices; and installing the main processor 
and associated surface equipment. Elec- 
trical checkout of the cable is necessary 
to ensure continuity and separation of 
the conductors prior to making final con- 
nections. Care must also be taken to 
ensure that the accessor trunk shield is 
tied to ground potential at only one 
place, usually at the central processor. 
Failure to do so may result in destruc- 
tive ground-loop currents. 

Cable should be placed along the mine 
back or rib in such a way as to avoid 
snagging by mine equipment. It is pref- 
erable not to run cable next to power or 
feeder cables in order to avoid stray 
electrical interference. Supporting 
strength of the cable and cable insula- 
tion type are determined by the particu- 
lar application. Since accessors are de- 
signed to function within 33 pet of 19 V 
dc, gauge of the power wires in the cable 
should be chosen to minimize voltage loss 
due to impedance. The cable supplied by 
Conspec uses 14-AWG power wires and indi- 
vidually shielded 18-AWG data wires in an 
overall shield with a common drain. This 
cable was found to be adequate in runs up 
to 3 km from the accessor trunk. Voltage 
boosters may be used to compensate for 
voltage loss due to longer runs. 

Accessors should be installed within 
proper distance limits to their field 
devices. Both accessors and field de- 
vices should be placed in protected areas 
to minimize accidental damage from per- 
sonnel and equipment. Accessors used by 



the Bureau were housed in waterproof 
metal enclosures; power and communication 
wires entered through military specifica- 
tion (MS) type connectors. 

Lightning protection devices should be 
installed where cable enters or exits 
mine buildings, shafts, or portals. Both 
primary and secondary protection are sug- 
gested by the manufacturer. 

Basic surface equipment consists of a 
central processor, printer(s), battery 
backup unit, and an accessor communica- 
tion trunk. Voltage regulation, noise 
suppression, or power conditioning de- 
vices may be required if voltage spikes 
are present on the 110-V ac power input 
to the processor. A hookup block diagram 
of the surface equipment is shown in 
figure 9. 

After connecting the accessor cable to 
the communication trunk, voltage may be 
measured at each accessor to check splice 
connections and also to ensure that prop- 
er operation voltage is present. At 
this point, an accessor check diagnostic 
can be used to check proper operation of 
each accessor before starting the main 
program. 

Once in the main program, system 
troubleshooting is simplified by using 
alarm states to diagnose problems. As an 
example, the Bureau often uses Bl-type 
accessors to monitor the power and sensor 
line condition of continuous radiation 
monitors. Low alarm limits are set for a 
value significantly below background 
count. Power failure to a monitor is 
then an alarm condition; a low alarm 
without a corresponding power-fail alarm 
may indicate an electronic malfunction in 
the monitor. 



18 



Battery 
backup 



110 V ac 

^ 



Voltage sensor 

and 

time delay 



+ 12 V dc 



"T ^Communication 
trunk 



Inverter 



110 V ac 



Spike 
protection 



110 V ac 



Power supply 



To acce ssors 
+ 24 Vdc 



Data 

-^ > 



Surge 
protection 



+ 24 
V dc 



Data I 



LL 



+ 24 V dc 



Line driver 
card 



110 Vac 



Printer 



Data 



Processor 



Data 



FIGURE 9. - Block diagram of surface equipment hookups. 



Communication failure alarms are also 
diagnostic in nature. They may be. caused 
by cable incontinuity , improper voltage 
to accessor, or accessor malfunction. 
Cable incontinuity would cause a C.FAIL . 
alarm to be generated for all accessors 
downstream. This narrows the fault to 
the area between two accessors: the last 



with communication and 
Low voltage commonly 
types of accessors (Bl 
may suspect recurring 
one accessor to be due 
repeated address or a 
malfunction. 



the first without. 

affects certain 

type) first. One 

C.FAIL alarms on 
to an accidentally 

possible accessor 



SYSTEM USE 



After a final checkout of both surface 
and underground connections, the user may 



start the system, enter 
and begin operation. 



the data base. 



19 



STARTUP PROCEDURE 

The following step-by-step procedure 
assvimes all connections have been proper- 
ly made. 

1 . Ensure that power is on to terminal 
and printer(s) . 

2. Turn on disk drive, insert system 
disk, and close drive door, 

3. "Cold boot" the system into the 
CP/M mode by performing the following 
steps: 

a. Push the reset button (rear of 

terminal) . 

b. Type the spacebar to obtain the 

CRT message 

MPS-92 
> 

c. Type the letter F. 

CP/M will now be loaded from the disk 
into RAM. After loading is complete, the 
CRT displays 

>FQCPM VI. 1 

A> 



5. After the main program is loaded, 
an initialized date and time appear on 
the CRT in addition to the message 

READ STATUS FRM DISK 



OPTION (Y OR N) 



X (flashing) 



On the first powerup after installation, 
probably no status information will have 
been stored on disk. In this case, re- 
spond "N" and press the return key. Sta- 
tus, or system configuration, must then 
be entered through the keyboard into mem- 
ory before it can be saved on disk. If 
status has previously been saved, respond 
"Y" to the prompt before pressing the re- 
turn key. This causes all system status 
to be loaded. 

From this point onward, all user com- 
mands consist of three-character mnemon- 
ics typed on the keyboard and followed by 
the return key. After a command is en- 
tered, the computer will prompt for 
further data. 

6. After the disk drive stops click- 
ing, remove the disk, and turn off the 
drive. An access code must now be en- 
tered in order to communicate further 
with the computer. Two access codes are 
available , which permit different levels 
of entry: lower (operator) and higher 
(supervisor) , 



The A> is known as the A prompt ("A" cor- 
responds to the disk drive designation) . 
The computer is now waiting for further 
user input. The user can now either per- 
form CP/M functions or enter into the 
main program mode as shown below. 

4. To enter the main program mode, 
type 

SUBMIT S 

and press the return key. This will 
cause the main program to be loaded, a 
process which takes about 1 min. During 
this time, the CRT will display files as 
they are being loaded. 



The lower level code allows the user to 
perform housekeeping functions oriented 
to system maintenance. These include 
editing the CRT display, editing the 
scan, commanding controllable points, 
making temporary changes in parameters, 
and requesting certain print routines. 

The supervisor code contains the opera- 
tor commands as a subset, and also allows 
this user to enter and delete points, 
control disk input and output , set up 
shift reports, program event sequences, 
and perform print routines. 



20 



After entry of the access code, an 
"ACCESS ALLOWED" message on the CRT noti- 
fies the user to proceed. 

7. Set the time with the STT command. 
Present time is entered in 24-h format. 

8. Set the date with the STD command. 
The new date and time will now be printed 
on the printer. 

DATA ENTRY 

The data base, or status, consists of 
all point parameters that may be saved on 
disk. This includes point numbers, ad- 
dresses, accessor trunk number, etc., as 
well as sequencing programs and times for 
shift report or trend log generation. 
These data are initially entered by the 
user through the keyboard with data entry 
commands such as NEW. The NEW command is 
used to enter specific accessor informa- 
tion such as point number, accessor type, 
address, trunk number, announcement op- 
tions, and other parameters. 

Parameters that allow conversion of 
analog data to engineering units and set 
alarm limits are also entered at this 
time. These parameters may be updated at 
any time with the CAP command. With this 
command, old values are displayed while 
the computer waits for new input. Values 
that the user does not wish to change are 
retained by pressing the SKIP key. 

Values for correction factor (CF) and 
offset (OFS) are actually entered into a 
memory reference table. These values may 
be referenced by more than one accessor. 
Up to 255 different CF and OFS factors 
may be stored in the table. 

The CFI and OFS commands are used to 
enter values into the reference table. A 
data entry format imist be observed. 



The format for correction factor (CFI 
command) is 

M*X.XX E SX, 

where M = multiplier (1, 2, or 4), 

X.XX = value between 0.00 and 
2.55, 

E = 10 (implied), to be raised 
to the power of SX, and 

SX = sign and exponent 
(-7 to +7). 

The offset entry format (OFS command) is 

S X.XXXX E SX, 

where S = sign (+ or -) , 

X.XXXX = value between 0.0000 and 
7.9999, 

E = 10 (implied), raised to 
the power of SX, and 

SX = sign and exponent 
(-7 to +7). 

After data entry is completed, the DSS 
and PCO commands may be used to verify 
proper entries. Each accessor must be 
entered in the scan with the EDS command 
before the processor will initiate comr- 
munication. Points can also be removed 
from the scan with this command for main- 
tenance or other purposes. 

OPERATION 

Valid user commands are given in ta- 
ble 3, An (s) next to the command de- 
notes it as supervisor-level only, and a 
(k) signifies that a special key also ex- 
ists for that command. 



21 



TABLE 3. - System commands sorted by function 



Description 



Command' 



Function 



Print routines: 
Trend log. . . . 



Accessor scan 
list. 



Descriptor list... 
Shift report 



Correction factor 
and offset table. 



Sequence program- 
ming units. 

Sequence triggers. 

Alarm summary 



Time and date, 



Commandable points: 
Binary point 
(B2, B22, B25 
accessors) . 



LTT, 

TREND HDG(k) 



ACC. 



DSS, 



TSR(s), 
SPN(s), 
REQ. 



PCO(s) 



PSQ(s) 



STP(s) 



ALS, 

ALARM SUMMARY (k). 

TIME AND DATE(k). 



COC, 

COMM BINARY (k). 



Used to enter point assignment and time 
period for trend log generation. Up to 10 
analog points are permitted, and time per- 
iod is variable from 1 to 99 min. The 
TREND HDG key will print a heading for the 
log. 

Produces printout of the scan list sorted by 
address and trunk number. This indicates 
which accessors are enabled in the scan. 

Prints point numbers, addresses, descrip- 
tors, and other data. 

Generates printouts of averaged values per 
point for up to 30 points. TSR is used to 
set printout times from 00 to 23 h (99 gen- 
erates a report each hour) . SPN assigns 
points to the report; REQ requests current 
shift report without reset of count or 
average. 

Prints desired range of correction factors 
and offsets in both machine and floating- 
point format. 

Prints desired range of SPU's. 



Prints sequence triggers by point number. 

Prints current alarms by point number and 
identifies alarm condition. 

Prints current time and date. 



Used to execute a mode change command on a 
binary point. A CRT and printer message 
will indicate result. 



Analog point 
(B26 accessor). 



CPA, 

COMM ANALOG(k). 



Changes output position of commandable ana- 
log point. A CRT and printer message will 

indicate result. 

^A (k) next to a command signifies that it is a special key function. An (s) de- 
notes it as supervisor level only. 



22 



TABLE 3. - System commands sorted by funbtion — Continued 



Description 


Command ' 


Function 


Status file editing: 






Descriptor change. 


DSE 


Allows descriptor change of any point. New 
descriptor must contain 18 characters 








(blanks are permitted). 


Analog parameter 
change. 


CAP 


Allows change of alarm limits , correction 
factor and offset reference numbers, units 








code, and other parameters for analog 






points. 


Correction factor 


CFI 


Enters correction factor into reference ta- 


entry and change. 




ble. Only properly formatted correction 
factors are accepted. 


Offset entry and 
change. 


OFS 


Enters offset into reference table. Only 
properly formatted offsets are accepted. 




New accessor data 


NEW(s) 


Enters accessor data into memory. 


entry. 


- 




Edit the scan 


EDS(s) 


Enables or disables accessors from the scan. 


Delete a point. . . . 


KIL(s) 


Removes a point from memory. 


Change access 
codes. 


EAC(s) 


Changes senior and junior access codes. 




CRT display editing: 






Auto screen roll 


ROL 


Automatically acknowledges and deletes old 
events from CRT alarm and event area to 


and acknowledge. 








make room for display of new data. 


Set time and date. 


STT, 


Used to enter time and date in numerical 




STD. 


format . The STD command generates a print- 
out after date entry. 


Immediate status 


ISR, 


Displays immediate status of any point at 


request. 


STATUS (k). 


the time command is issued. This display 
' is not updated. 


Clear CRT screen. . 


CRT 


Clears CRT screen. Only updated data will 
reappear. 






Continuous status 


CSl to C26 


Enters and deletes points in status display 


monitoring. 




area on lower part of CRT. 


Disk status: 






Save status on 


SVD(s) 


Saves current status on nonvolatile disk 


disk. 


wr*A^\Vir/ * ••• •• • • • •• 


memory . 


Read status from 


RDS(s) 


Loads status from disk into memory. 


disk. 


j.*-fc-» i-f\*<^/9mm9 mm m •• •• 


Format a disk 


FMT(s) 


Formats a new disk to be compatible with 
system. 







'A (k) next to a command signifies 
notes it as supervisor level only. 



that it is a special key function. An (s) de- 



23 



URANIUM MINING APPLICATIONS 



The computerized system investigated 
offers many advantages to the uranium 
mining industry, particularly in the use 
of its monitoring and control capabili- 
ties. The system requires only a four- 
wire cable between the main processor and 
the accessors to provide 24-V dc power 
and communication. This cable may be 
wired in parallel, series, or branched to 
allow for accessor installation over dis- 
tances of up to 3 km from the central 
processor. Longer distances may be 
achieved through the use of voltage 
boosters and modems. Up to 128 accessors 
may be used per trunk line, and up to 
four of these lines are supported by 
hardware and software, for a total 
capacity of 512 accessors. These acces- 
sors can be interfaced to most stationary 
mine equipment for monitoring or control, 
including fans , pumps , radiation detec- 
tors, air doors, and anemometers. 

The system's monitoring capabilities 
may be used to keep records , initiate 
command sequences, and assist in trouble- 
shooting the system and its interfaces. 

RECORDS 

Recordkeeping is automatic for all 
changes of state or alarm occurrences. 
The operator is notified of these occur- 
rences at the console so that remedial 
action can be taken if necessary. This 
can be applied to continuous radiation 
monitoring as well as to keep track of 
air door positions or the operational 
status of fans or other motors. In radi- 
ation monitoring, a rate alarm may be set 
to warn of rapidly changing conditions 
before critical exposure levels are 
reached. Shift reports may be used as an 
aid in figuring average working level 



exposure in monitored areas . Trend logs 
may be used to study radiation variation 
in connection with mining activity or 
environmental changes . Studies such 
as these may improve ventilation effec- 
tiveness and thereby reduce ventilation 
costs. 

SEQUENCES 

Command sequences can be constructed 
for either manual or automatic operation. 
This feature may be used to turn on, or 
off,- a number of fans from the console in 
a predetermined sequence with time delays 
between steps. Status monitoring then 
gives feedback to inform the operator of 
command execution and if indeed the fans 
went to the commanded state. Anemometers 
interfaced to the system would give 
further verification of ventilation flow. 
In monitoring mine power with the system, 
the above sequence could be set to auto- 
matically start fans after a power out- 
age. Other sequence applications include 
warning personnel of imminent fan or 
motor startups or high radiation levels , 
and controlling fans based on radiation 
readings . 

Troubleshooting the system hardware 
(cables, accessors, and field devices) is 
aided by using the system's monitoring 
capabilities. Certain types of alarms 
may be used to diagnose hardware problems 
and to narrow down their locations. 
Basic hardware problems that will be de- 
tected by the system include broken trunk 
line, broken sensor line between accessor 
and field device, power failure for field 
devices, and certain electronic malfunc- 
tions in field devices such as radiation 
monitors . 



CONCLUSIONS 



With continually changing radon daugh- 
ter concentrations present in underground 
uranixim mines, minimizing worker exposure 
can be difficult. The system described 
in this report has the capability to con- 
tinuously monitor critical situations 
such as fan operation and radon daughter 
concentrations and to alert the ventila- 
tion engineer when excessive measurements 



are present. It also has the capability 
to control ventilation, sound underground 
warnings, and automatically restart fans 
after power failures. Recordkeeping fea- 
tures of the system will help the venti- 
lation engineer to control radiation haz- 
ards and to predict where future problems 
may occur. 



24 



REFERENCES 



1. Archer, V. E. Statement on the Ra- 
don Daughter Standard and Changes Pro- 
posed by MESA. Testimony before the Fed- 
eral Metal/Nonmetal Mine Safety Advisory 
Committee, Seattle, WA, Oct. 26-28, 1976, 
8 pp.; available upon request from Spo- 
kane Res. Cent., BuMines, Spokane, WA. 



6. Franklin, J. C. Control of Radia- 
tion Hazards in Underground Uranium 
Mines. Paper in Proc. Radiation Hazards 
in Mining: Control, Measurement, and 
Medical Aspects, Oct. 4-9, 1981, Golden, 
CO. Soc. Min. Eng. AIME, 1981, pp. 441- 
446. 



2. Bates, R. C. Ventilation Cost Im- 
pact of Reduced Radon Daughter Working 
Levels. Paper in Proc. Radiation Hazards 
in Mining: Control, Measurement, and 
Medical Aspects, Oct. 4-9, 1981, Golden, 
CO. Soc. Min. Eng. AIME, 1981, pp. 1066- 
1070. 

3. Franklin, J. C, T. 0. Meyer, R. W. 
McKibbin, and J. C. Kerkering. A Contin- 
uous Radon Survey in an Active Uranium 
Mine. Min. Eng. (N.Y.), v. 30, No. 6, 
June 1978, pp. 647-649. 

4. Musulin, C. S., J. C. Franklin, and 
F. A. Roberts. Effects of a Fan Shutdown 
on Radon Concentration in a Positive 
Pressure Ventilated Mine. BuMines RI 
8738, 1982, 10 pp. 

5. Musulin, C. S., J. C. Franklin, and 
V. W. Thomas. Effects of the Diurnal Cy- 
cle and Fan Shutdowns on Radon Concentra- 
tion in an Experimental Uranium Mine. 
BuMines RI 8663, 1982, 13 pp. 



7. Droullard, R. F., and R. F. Holub. 
Continuous Working-Level Measurements Us- 
ing Alpha or Beta Detectors. BuMines RI 
8237, 1977, 14 pp. 

8. Shaw, D. M. , and J. C. Franklin. 
Continuous Area Monitoring and Alarm Sys- 
tem. Eng. and Min. J,, v. 183, No. 5, 
May 1982, pp. 84-90. 

9. Conspec Controls, Ltd. (Downs- 
view, Ontario, Canada). Senturion-200 
Hardware and Software Reference Manuals, 
1982 versions. 

10. Zaks, R. The CP/M Handbook with 
MP/M. Sybex, Inc., Berkeley, CA, 1980, 
321 pp. 

11. Franklin, J. C, R. J. Zawadski, 
T. 0. Meyer, and A. L. Hill. Data- 
Acquistion System for Radon Monitoring. 
BuMines RI 8100, 1976, 19 pp. 



25 



APPENDIX. —ANALOG ACCESSOR CALCULATIONS 



Data returned from analog accessors, 
depending on the accessor type, contain 
either one or two bytes of digitized ana- 
log data. The computer processes these 
data for alarms and uses a single- 
precision math routine to convert to en- 
gineering units for printout and display. 
Initially, the user is required to calcu- 
late and enter parameters that are used 
by the system to determine alarms and to 
convert accessor values to engineering 
units. These parameters may be saved as 
status on disk and read into memory upon 
later startups. The basic equation used 
by the processor is 



Correction factor and offset are calcu- 
lated from these values as follows: 



FP = R * CF + OFS, 



(A-1) 



where FP = floating point value for 
display, 

R = accessor value, 

CF = correction factor, 

and OFS = offset. 

The accessor value is the returned 
data from eight-bit accessors or the 
eight most significant bits from pulse- 
integrating (PI) accessors. Because PI 
accessors have additional hardware fac- 
tors involved (selectable count period 
and prescaler) , their calculations are 
slightly different and will be covered 
later. 

EIGHT-BIT ACCESSORS 

To calculate the correction factor and 
offset for A5 or A8 accessors, the values 
to be displayed at the minimum and maxi- 
mum imputs must be known. For the A5 
accessor, this represents the values at 
V dc (minimum input) and 5 V dc (maximum 
input). For the A8 accessor, this repre- 
sents the values at ohms resistance of 
the remote potentiometric sensor (minimum 
input) and 2,000 to 10,000 ohms full- 
scale resistance of the remote potentio- 
metric sensor (maximum input). 



and 



CF = 



OFS = Vmin, 
Vmax - Vmin 



255 



(A-2) 
(A-3) 



where OFS = offset, 

CF = correction factor, 

Vmin = value to be displayed at 
minimum input , 

and Vmax = value to be displayed at 
maximum input. 

Alarm limits are calculated in machine 
units for data entry reasons. These can 
be obtained by substituting desired alarm 
limit values (for FP) into equations A-4 
and A-5 to calculate for the accessor 
value (R) as shown below: 

FP(L) = R(L) * CF + OFS, (A-4) 

and FP(H) = R(H) * CF + OFS, (A-5) 

where FP(L) = floating point low alarm 
value , 

FP(H) = floating point high alarm 
value , 

R(L) = low alarm limit in ma- 
chine units, 

and R(H) = high alarm limit in ma- 
chine units. 

Values obtained for alarm limits , R(L) 
and R(H) , are rounded to the nearest 
whole number for machine entry. An exam- 
ple analog calculation is shown below, 

A J-Tec anemometer is to be used to 
measure air velocity in a drift. Since 
the J-Tec has an analog voltage output , 
it will be used with an A5 accessor. The 
following information is known: 



26 



1. J-Tec VA-215 anemometer output is 
from to 5 V dc, corresponding to air 
velocity from to 1,500 ft/min. 

2. The desired alarm limits are 

Low limit = 100 ft/min. 

High limit = 1,000 ft/min. 

Determine (1) CF and OFS and (2) alarm 
limits for machine entry (R values): 

1. CF and OFS: 

From equation A-3: 



^ Vmax - Vmin ^ 1,500 - 
255 255 



= 5.88. 

From equation A-2: 

OFS = Vmin = 0.00. 

2. Alarm limits: 

Low alarm (100 ft/min) 

From equation A-4: 

100 = R(L) * 5.88 + 0; 

R(L) = 17. 

High alarm (1,000 ft/min) 

From equation A-5: 

1,000 = R(H) * 5.88 + 0; 

R(H) = 170. 

PULSE-INTEGRATING ACCESSORS 

The following discussion pertains to a 
PI accessor interfaced to a continuous 
radiation monitor such as a radon or 
working level monitor. 

The continuous radiation monitor 
outputs random electrical pulses 



corresponding to radiation input. PI ac- 
cessors accumulate a count of these 
pulses for a preset time period. Accu- 
mulated pulses are converted to radiation 
concentrations such as picocuries per 
liter or working levels by the equation 

RC = ^^-^^ * DF 



C * DF B * DF 



(A-6) 



where RC = radiation concentration, 
C = gross accumulated pulses , 
B = background (per period T) , 
T = present count period, 

and DF = calibration factor. 

The PI accessor divides incoming pulses 
by a prescaler value and accumulates the 
result for a period of time (T) . At the 
end of T, this result (the accessor val- 
ue) is latched and supplied to the pro- 
cessor upon interrogation. At the end of 
each T, the old value is replaced by a 
new one. 

Prescaler Value 

The relationship between accessor value 
and actual count is 



where 



and 



R = C/P, 

R = accessor value, 

C = count from radiation 
monitor , 

P = prescaler value. 



(A-7) 



Although the maximum accessor value is 
software-limited to 37,767, the optimum 
range of R in consideration of processing 
speed is 



256 < R < 512. 



(A-8) 



27 



Therefore, under normal radiation condi- 
tions, the accessor will be set up so 
that the prescaler value is in the range 



256 < C/P <> 512 
(desirable condition). 



(A-9) 



Furthermore, the prescaler value must be 
an integer between 2 and 255, inclusive. 
This value is set as a binary number on 
dipswitch S22. 

Correction Factor, Offset, 
and Alarm Limits 



Example PI Calculation 

In this example, a calibrated working 
level monitor has been installed in a 
mine heading. The desired sample time is 
5 min. The following information is 
known: 

1. Average background count in the 
heading is 5,500 counts per 5 min, 

2. The detector calibration factor 
(DF) is 6.7 E-4 WL-min per count. 

3. The desired alarm limits are 



The CF and OFS values are used by the 
processor to convert the R value to radi- 
ation concentration (RC). Equation A-1 
is used in this operation, and the float- 
ing point value to be found is RC: 

RC = R * CF + OFS, 

where RC = radiation concentration 
(floating point value), 

R = accessor value, 

CF = correction factor, 

and OFS = offset (may be positive or 
negative) . 

By substituting with equations A-6 and 
A-7 and rearranging terms , a similar form 
can be obtained: 



RC = R * 



(P * DF) (B * DF) 



(A-10) 



Therefore, for the continuous radiation 
monitors , 



CF = 



P * DF 



and 



OFS = - 



(B * DF) 



(A-11) 



(A-12) 



The background (B) and count (C) terms 
in the above equations are averaged val- 
ues obtained during monitor calibration. 



Low limit = 2,750 counts per 5 min 
(one-half of background). 

High limit =1.0 WL. 

Determine (1) optimum prescaler value, 
(2) CF and OFS, and (3) alarm limits for 
machine entry (R values): 

1. Optimum prescaler value: 

The "normal" expected radiation 
concentration ranges up to 1 WL; 
therefore, count at 1 WL is found 
from equation A-6: 

1 WL - ^'= - l'^""'' * (6.7 E-"). 

C(l WL) = 12,962 counts. 

Prescaler range from equation A-8 
is 



12 962 
256 < ^ ;^°^ < 512; 



therefore, 25 < P < 50. 

A moderate value, P = 40, is then 
chosen. 



2. CF and OFS: 

From equation A-11: 

40 * (6.7 E-4) 



CF = 



= 5.36 E-5. 



28 



From equation A-12: 

OFS = - 5,500* (6.7 E'M 

= - 7.37 E-^ 

3. Alarm limits: 

Low alarm (one-half of background 
= 2,750 counts) 



From equation A-7: 

R(L) = 2,750/40 = 69. 

High alarm (1.0 WL) 

From equation A-1: 

1.0 WL = R(H) * (5.36 E'^) 

- (7.37 E-1) , 
R(H) = 324. 



INT.-BU.OF MINES,PGH.,PA. 27 566 








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